Why did the Minister for Magic never just ask the muggle Prime Minister if he would get the SAS to snipe Voldemort?
No, seriously, Voldemort represented the greatest threat to not only the magical community of the British Isles but also the world since nearly everything he did violated the Internation Statute of Secrecy. The existence of such a thing means there is some for of international wizarding government, probably similar to the real-world UN, and so that puts Voldemort on the same level as someone like Saddam Hussein, or to put it another way, a man who absolutely must be dealt with as swiftly and decisively as possible. We know that the Minister for Magic is in contact with the Prime Minister (technically his title means he works for the Prime Minister) and we also know that Voldemort does not fear muggles. The whole franchise revolves around his prejudices and how wrong they are, so if anyone was vulnerable to attack by muggles it's Voldemort. Even if he was looking at a full battalion he wouldn't feel threatened, that's how inferior he thought they were. So get the muggles to fight him, he'll never expect it and if, by some miracle, he did he wouldn't take it seriously and still leave himself vulnerable. His magical spells and barriers can't stop physical objects, if they could then Nagini would never have been killed by a sword. A bullet is a physical object. And you apply a bullet directly to the forehead from a seriously long way away. So we have a Dark Lord of the Magics who:
1) Does not fear muggles and views then as no threat, therefore underestimates them and is vulnerable to them
2) Cannot block physical objects unless he has the reflexes to react to such, which he doesn't because he's 60+ years old and the object in question is a bullet
3) Must be destroyed by any means possible because of the threat he poses to the international community
So get a muggle to snipe the guy. He'll never expect it and he can't block it. Arrange a trap. Get the Order of the Phoenix to use Harry Potter as bait or something, get Voldemort into position and then have an SAS shapshooter take him out with a single round. Even if he has horcruxes left this would buy you the time needed to go hunt them down in relative safety. Voldemort will probably try to return again but by then he shouldn't have any horcruxes left so just shoot him again and be done with it. Crisis over.
This is just indicative of a wider issue I have with the Harry Potter universe, that even the good, kind and friendly wizards, like Dumbledore or Hagrid, devalue muggles and view them as inferior. Sure they may not try to actively torture or kill muggles but they see them as basically helpless in comparison to magical folk. A well placed sniper round to Voldemort's temple would end the crisis but does anyone think to even ask the muggles? Noooo. Even the great and wonderful Dumbledore never for one second considers that they might actually have something to offer. It wouldn't even breach the secrecy of their world. The Prime Minister already knows and he wouldn't even need to tell the few people involved in the assassination that they were taking out a wizard. If they saw Voldemort perform some magic, so what? Get these men to comply to the Official Secrets Act. That's right, muggles have laws about keeping secrets just like the wizards. Guess we're not so different afterall.